Semiconductor devices having a device structure portion (e.g., a structure of a light-emitting element) formed by stacking an AlGaN semiconductor layer on a substrate made of sapphire or on a template having the substrate have conventionally been produced. The semiconductor devices described above include the one in which, after the device structure portion is formed on the substrate or on the template, the substrate is removed (lifted off) from the device structure portion or the template. By lifting off the substrate, the heat radiation performance of the device structure portion can be enhanced, the efficiency of extracting light generated on the device structure portion can be enhanced, and a vertical structure (a structure having a pair of electrodes on and under the device structure portion) can be realized.
As a method of lifting off the substrate, Patent Document 1 proposes a method of lifting off the substrate by a process in which a laser light is emitted from the side close to the substrate, and the laser light is absorbed by a predetermined layer on the substrate to chemically decompose the layer. Specifically, the Patent Document 1 describes the method described below. In this method, a GaN layer absorbs the laser light, and then, the GaN layer is heated, whereby the GaN layer is decomposed into Ga and N2. Ga deposited by the decomposition is melted, whereby the substrate is lifted off.
However, as pointed out in Non-Patent Document 1, the lift-off utilizing the mechanism similar to the GaN layer proposed in the Patent Document 1 is impossible in an AlN layer and AlGaN layer. The Non-Patent Document 1 proposes a method of mechanically lifting off a sapphire substrate and an AlN layer, which is formed on the sapphire substrate, by deforming an AlN/AlGaN superlattice layer through the absorption of laser light (wavelength: 268 nm). The laser light (wavelength: 286 nm) passes through the sapphire substrate and the AlN layer, but is absorbed by a miniband of the AlN/AlGaN superlattice layer.